Vacuum casting apparatus.



J E. DUNN.

VACUUM CASTING APPARATUS.

APPLICATION man AUG.20. 1915.

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VACUUM CASTING APPARATUS.

APPLICATION FILED AUG.20. 1915.

1,1 86,558. Patented June 13, 1916.

2 SHEETSSHEET 2- wn'NEssEs INVENTOR %%%%M W 5% nn sra'rns rnrnnr o l JAMES E. DUNN, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR 'IO LEE S. SMITH AND SON MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

. VACUUM CASTING APPARATUS.

masses;

Specification of Letters Patent. P t m June 13, 191

Application filed August 20, 1915. Serial No. 46,503.

To all whom it may concern:

Be it known that 1, James E. DUNN, a citizen of the United States, and a resident of Pittsburgh, in the county of Allegheny and State of- Pennsylvania, have invented a new and useful Improvement in Vacuum Casting Apparatus, of which thefollowing is a specification.

This invention relates to vacuum casting apparatus for producing dental inlays.

The object of the invention is to provide improved apparatus for casting an accurate dental inlay which completely fills the molding cavity and does not have imperfections which might produce a leaky filling.

A further object of the invention is to provide apparatus of this kind which is of simple construction and can be readily manipulated during the casting operation, which enables molds ofi'various sizes to be used with the same machine, which is so arranged as to enable the operator at any time to know the degree of vacuum produced in the machineand tobe imposed upon the investment, and which enables the degree of vacuum to be adjusted to the most eiiicient point.

Further obiects of the invention are in part obvious and in part will appear more in detail hereinafter.

The invention comprises the vacuum casting apparatus hereinafter described and claimed.

In the drawings, Figure 1 is a frontelevation of one form of apparatus embodying the invention, parts being broken away and the mold flask being shown in section; Fig. 2 is a detail sectional elevation of the rear portion of the apparatus, and showing the heating burner; Fig. 3 is a sectional plan view on the line 33, Fig. 1; Fig. 4 is a sectional elevation through the base, on the line 4-4, Fig. 3; Fig. 5 is a, detail view of a safety plug; Fig. 6 is a cross sectional view of the valve, the section being taken on the line 6-6, Fig. 7; Fig. 7 is a longitudinal section of said valve on the line 7 -7, Fig. 6; Fig. 8 is a detail sectional view of a vacuum regulating valve; and Fig. 9 is a detail sectional elevation of another valve.

The apparatus illustrated in the drawings comprises a suitable supporting base or foundation 1 carrying the statlonary part of the apparatus, andwhichmay rest upon a table or other support. On sald base are mounted two casting tables 2 located at opposite sides of the machine, and preferably of different sizes in order to receive difi'erent casting molds. Each casting table is in the form of a metal disk having an upwardly extending circular projection 22 with a flat upper surface and providingv an annular vertical shoulder 21 and an annular plane surface 20 to receive the molding flask 14, in which is located the moldbody or investment 13 containing the cavity 13 to produce the inlay. This investment'13. is made in the usual manner and is provided with a gate 13 communicating with a cavity or depression 13 in its upper end to receive the metal to be melted for filling the cavity and producing the inlay.

The tables 2 are threaded upon the upper ends of pipes 15 and are provided withcentral openings 2 'communicating' with the passages in the pipes 15 for imposing suction or vacuum upon the lower surface of the porous investment for causing the molten metal to be drawn into and completely fill the cavity 13. Preferably, the investment 13 is formed with a shallow cavity 13 in its bottom so that the vacuum is effective over a large area of the investment and is not concentrated at the central axis thereof directly beneath the cavity 13*,while the investment and flask have a three point bearing upon the plane surface 20, the shoulder 21 and the proljection 22 so as to produce an effective sea The two vertical pipes 15 communicate with horizontal pipes 16 connected to opposite sides of a three-way valve 5 shown in detail in F igs, 6 and 7. Said valve has a casing 25 in which is a cavity to receivev a conical plug 26 held therein by a screw cap 30 and having a stem 29 to which is connected an operating handle 4 lying on the outside of the 'base 1. The plug 26 has a longitudinal bore 26 open at one end and communicating through the casing with a pipe 19, and a port 28 through its side wall which is adapted in the three several positions of the valve to communicate with either of two passages in the casing 25 leading to the pipes 16 and casting tables 2, or

with an air inlet passage 27 in the upper porcommunicates with suitable so as to actuate the gage and register the vacuum thereon. In the form shown, this valve comprises a casing 34 screwed into an opening in the base 1 directly above the valve inlet 27 and in the bore of which is a vertically movable stem 33 provided at its lower end with a valve member 32 and at its upper end with an operating button 35. The valve is normally held in the position shown in Fig. 9, in which position the passage 27 is opento atmosphere, by a compression spring 36, so that the button 35 must be pressed downwardly wheneverit is desired to close the inlet passage 27 independently of valve-5..

Pipe 19 communicates through a vertical pipe 31, with a suitable vacuum gage 6, which is preferably of a type to indicate the vacuum in inches of mercury, or some other suitable units. Pipe 19 also extends out through the rear wall of the base 1 and devices for regulating the vacuum to be produced.- As illustrated, said pipe communicates-with a T 40, onenbranch of which has screwed therein a casing 41provided with a cavity 42 to receive a needle valve 43 threaded into saidcasi and provided with ahead 44. Casing 41 1s also provided with one or more lateral ports or openings 45. By adjusting the valve member 43 by its head 44 the pas-v sage through the regulating valve maybe opened more or less to admit air to the pipe 19. The other branch 'of the T 40 communicates with a flexible conduit, such as the rubber tube 10, leading to the suction end of a vacuum producing machine, such as the rotary pump 9 provided with an operating pulley which may be coupled by a belt or other device to an electric motor or other operating mechanism, (not shown). The discharge end of said pump communicates through a rubber tube or other flexible conduit 12 with a suitable blow-pipe 11 having a connection 39 communicating with a source of fuel supply. At the back of the base 1 is located an upright stationary standard 7 provided with an adjustable bracket 7 a to receive the investment in baking or burning the same, and below said bracket is located a suitable burner, such as the Bunsen burner 8, having the usual regulating devices and communicating with a gas supply.

' In operation, the tooth cavity is filled with a brittle wax, to which is connected a thin metal stem for producing the gate '13". The wax impression is surrounded with suitable investment material to form the investment 13, which is properly shaped to provide the cavities 13 and 13. The flask 14 with the investment therein is then placed on the bracket 7 over the burner 8 and is heated to burn or vaporize the wax and produce the cavity 13. The invest ment in its flask is then placed on one of the tables 2 in the manner shown in Fig. 1, and the gate forming pin is removed.

The operating motor is started to drive the pump 9 and produce a suction effect in the pipe 10 and a pressure effect in the pipe 12. The valve 5 is in its middle or neutral position, so that the port 28 in said valve communicates with the passage 27 leading to atmosphere. Consequently, the suction end of the pump is open through a large passage to the atmosphere and a full supply of air is delivered by said pump to the blow pipe 11. The gold to form the inlay is placed in the cavity 13 the supply of gas through the pipe 12 is turned on, and the blow pipe flame is directed upon said gold to melt the same. This gold is drawn into the cavity by the suction of the pump 9, which'is applied to the investment by turning the, operating handle 4 so as to connect the pump through the valve 5 with the proper casting table 2. The suction is applied at a-time when the gold is in a completely molten condition, so that it will flow freely and smoothly into the cavityunder the influence of the suction. In practice, however, it is found that too great a vacuum applied to the investment may produce an imperfect inlay, by causing the gold to flow prevents escape from the cavity 13 of all the air therein, so that bubbles may be produced in the inlay. Consequently, the operator should know what degree of vacuum is being produced by the pump before the vacuum is applied to the investment. This is ascertained by pressing down the button 35 to close the valve member 32 against its seat on the upper end of the casing 25 and thus shut off the supply of air through the pipes 19 and 15 leading to the suction end of the pump. The vacuum produced by the pump then becomes efl'ective upon the gage 6, the pointer of which indicates the vacuum in inches of mercury. It the vacuum is too high the regulating valve is opened by turning its head 44 so as to admit a supplemental air supply to the pipe 10 communicating with the pump. The greater the supplemental air supply through this regulating valve, the less efiective is the vacuum upon the gage 6. The regulating valve. is adjusted so that the most efiective vacuum is produced by the pump. This regulating valve can be located anywhere between the casting tables 2 and the suction side of the pump. The operator now releases the valve head 35 so that the valve 5 is again open through the passage 27 to atmosphere. As soon as the gold is fully melted, the operating handle 4 is turned. in the proper direction to connect the particular casting table in use to the pump, to thereby apply the vacuum to the investment. This vacuum so rapidly that it chokes the gate 13" and causes the gold to flow into the cavity, which it fills completely, and there solidifies. During adjustment of the regulating valve and while casting, the blow pipe receives its supply of air from the regulating valve and through the pores of the invest ment so that the molten metal has no opportunity to cool or solidifyuntil it reaches the cavity 13.

In some cases theinvestment has a flaw or is weaker than usual,'s0 that it breaks during the casting operation, which allows the molten gold to flow down throu h the investment and into the pipe v15. Ihis gold is caught by a suitable trap, shown as a hollow plug 24 screwed into therbottomof a T connection 23 between the pipes 15 and 16. This plug can be removed at intervals for recoveringthe gold.

The apparatus described is of simple.construction and can be readily operated in a most efiicient manner. It enables a proper degree of vacuum to be applied to the investment and thereby produces a very accurate and perfect inlay.

"What I claim is 1. Vacuum casting apparatus, comprising acasting table, a source of vacuum therefor, a vacuum indicatin gage communicating with said source, a va ve for controlling communication between said table and'source,

and a valve controlling communication between said source and the atmosphere.

2. Vacuum casting apparatus, comprising a casting table, a source of vacuum therefor, a vacuum indicating gage communicating with said source, a valve for interchangeably connecting said source to said table or an air inletyand a valve for closing said air inlet.

3. Vacuum casting apparatus, comprising a plurality of castlng tables, a source of vacuum therefor, a vacuum indicating gage communicating with said source, a valve for interchangeably connecting said source .to any of said tables or an .air inlet, and a valve controlling communication between said source and the atmosphere,

4. Vacuum casting apparatus, comprising a plurality of castmg tables, a source of .vacuum therefor, and a single valve arranged to establish communication between any one of said tables and said source of vacuum, or to connect said source of vacuum to the atmosphere.

5. Vacuum .castin apparatus, comprising a plurality of casting tables, a source of vacuum therefor, a gage communicating with said source of vacuum, means for establishing communication between saidtables and the source ofvacuum, anair inlet for said source of vacuum, and means for closing said inlet to actuate said gage.

6. Vacuum casting apparatus, comprising means for closing said'inlet.

8. Vacuum casting apparatus, comprising a casting table, a source of vacuum therefor,

an air inlet for said source, means for establishing communication between said source and either said table or said inlet, and a valve between said table and source of vacuum and controlling an air supply for said source independent of said air inlet and table.

9. Vacuum casting apparatus, comprising a casting table, a source of vacuum therefor, an air inlet for said source, means for closmg said air inlet, and means inde endent of said air inlet and table for supp ylng additional air to said source.

10. Vacuum casting apparatus, compris ing a casting table, a source of vacuum therefor, a gageconnected to said source, an air *inlet to said source, means for closing said inlet to actuate the gage, and means for supplying additional air to said source.

11. Vacuum casting apparatus, compris ing a casting table, a source of vacuum connected thereto,- an air inlet for said source, means for closing said inlet, and an adjustable valve for controlling a supplemental air supply independent of said air inlet and table to said source.

12. Vacuum casting apparatus, comprising a casting table, a source of vacuum therefor, a gage connected to said source, an air inlet to said source, means for closing said inlet'to actuate the gage, and an adjustable valve for controlling a supplemental air su ply to said source.

13. acuum casting apparatus, comprising a casting table having an annular'plane surface and an upwardly extending projection forming a shoulder, a molding flask resting upon said surface and surrounding said projection and abutting said shoulder and an investment of porous material in said flask having an exposed bottom cavity above said projection. I I

In testimony whereof, I have hereunto set my hand.

JAMES E. DUNN. Witnesses:

Emsnur In. HYDE, Snn'B. Fnrrz. 

